Conventional commercial drying tumblers expose a wet load of laundry to a cross flow of warm air which expedites the evaporation process and also carries water vapor out of the system. A conventional drying tumbler generally includes a drum or drying chamber that has a cylindrical drum wall which is perforated with a plurality of holes. The front of the drum includes a loading door that can be opened to permit the loading of laundry items but seals to form a solid barrier when the door is closed. The rear of the drum also comprises a solid wall. In order to tumble the load of laundry items, the drum is rotatable and has a series of ribs or baffles on the interior of the cylindrical drum wall which carry the load to an elevated point within drum so as to facilitate the tumbling action.
To introduce heated air into the drying chamber, a heat source is mounted above the drying chamber. A blower is arranged below the drying chamber which creates a negative pressure beneath the drying chamber and thereby draws heated air through the rotating drum via the perforations. To isolate the drying chamber from atmospheric pressures and temperatures, an outer stationary cylinder surrounds the drying chamber. The space between the outer cylinder and the rotating drying chamber, however, permits a large amount of heated air to pass around the drying chamber and thereby bypass the wet load of laundry. Consequently, cross-flow type drying tumblers are inefficient, as significant amounts of the heat input and air flow do not help advance the drying process, resulting in increased energy consumption.
More recently, drying tumblers have been developed which utilize an axial flow design in which the air flows through the drying chamber generally parallel to its axis of rotation. This type of drying tumbler eliminates the inefficiencies found in the cross flow type tumblers by utilizing a series of seals and chambers which force all of the air flow through the laundry load. Therefore, axial flow drying tumblers dry the laundry items faster and consume less energy than cross flow type tumblers. With an axial flow drying tumbler, the air flows through the drying chamber at a substantial velocity and therefore tends to blow the laundry items towards the front of the drying chamber. In most circumstances, this mixes the load thereby helping to eliminate hot or wet spots.
This blowing of the load towards the front of the drying tumbler, however, can lead to potentially serious problems when drying large items such as sheets or blankets. In particular, as they blow forward, items like sheets or blankets can open up like a parachute and end up blocking the openings through which the heated air is drawn out of the drying chamber. As a result of the blockage, the vacuum at the air exit openings in the drying chamber builds up, causing the load to be held tightly against the cylindrical wall of the drying chamber. This prevents the load from tumbling and the resultant build-up of heat will eventually lead to permanent wrinkling, scorching or other damage to the items in the load.